Economical impact resistant compression molded door

ABSTRACT

Improved synthetic doors having high impact resistance employ SMC skins having a layer of reinforcing extending throughout each skin, which skins are glued to rectangular frame forming the rails and stiles of said door and the cavity between the skins filled and a plastic foam. The process of making the doors include the steps of placing a layer of SMC in a compression mold, placing a flexible reinforcing sheet over this layer of SMC so that it covers the entire skin area, placing a second layer of SMC over said reinforcing sheet and curing said layers under heat and pressure in such mold to form the impact resistant skin.  
     The door defined along can include a window light also having high impact resistance wherein the window light includes a sheet of tempered glass adhered to a sheet of polycarbonate, second sheet of tempered glass and a specific frame separating the two sheets of tempered glass along with a seal means about the perimeter of this assembly, so that the frame and sealing means will allow the perimeters of the sheets to articulate when the central portions of the panes flex.

BACKGROUND

[0001] Synthetic doors formed with skins of sheet molded compositions [SCMs] mounted on a rectangular frame have proven to be satisfactory in many residential and commercial applications. Typically such doors have the skins or panels which are glued to a rectangular frame formed of the rails and stiles of such synthetic doors. Such doors are illustrated in U.S. Pat. No. 5,934,040 issued to Chen and U.S. Pat. No. 4,550,450 issued to Thorn. The hollow interior of these structures are filled with a foam, such as polyurethane foam, and the outer surfaces of the skins can include wood graining so that the finished door looks very much like a conventional wooden door. Moreover since these synthetic doors have dimensional stability, which resist deflection and warping, along with being insect and mold (mildew) resistance, they are highly competitive with conventional wood doors.

[0002] While such synthetic doors meet most building code requirements, such doors do not meet more stringent requirements for exterior doors in some states, such as those of Dade County in Florida. This county has issued PA 201 Impact Test Procedures, PA 202 Criteria for Testing Impact and Non Impact resistant Building Envelope Components Using Static Air Pressure and PA 203 Criteria for Testing Products Subject to Cyclic Wind Pressure Loadings in response to the extreme weather conditions experienced in Florida, commonly referred to as tornados and hurricanes.

[0003] An object of this invention is the provision of synthetic doors of the type described which meets the criteria of Dade County. Actual tests by Dade County on the doors constructed according to this invention have passed the above referenced tests.

[0004] Cyclic loading on synthetic doors under the Dade County criteria, not constructed according this invention, experienced failures when tested. While the exact cause of the failures of the prior art synthetic doors have not been determined, studies have been made of stresses leading to failure in SMCs products, such as Toughness of short fiber composites. An approach based on crack-bridging by Patrik Fernberg, Division of Polymer Engineering Department of Applied Physics and Mechanical Engineering Luleå University of Technology, SE-971 87, Luleå, Sweden. Since the prior art SMCs use short glass fibers usually less than two inches in lenght for reinforcing SMCs this study sheds some light on why the prior art synthetic doors failed to pass the criteria for Dade County. In part the study points out, the prior art skins are likely to develop a number of inelastic failure mechanisms from debonding, microcracking, fiber failure and fiber pull-out which occur prior to a cracking of the skins.

[0005] Another object of this invention is to address the above failure modes in the skins of an exterior synthetic door without making the doors economically challenged in the market place.

[0006] Still other objects will be apparent from the written description and drawing of this specification.

SUMMARY OF THE INVENTION

[0007] According to this invention an improved synthetic door having high impact resistance includes a rectangular frame forming the rails and stiles of said door, a pair of skins, one skin glued to one side of the frame and the other skin glued to the other side of the frame forming a hollow cavity between the skins and the inside perimeter of the frame, each skin being formed with a flexible sheet reinforcing sandwiched between layers of SMC when cured and a plastic foam filling such cavity.

[0008] Also this invention teaches the method for forming the impact resistant skins by the steps of placing a layer of SMC in a compression mold, placing a flexible reinforcing sheet over this layer of SMC, placing a second layer of SMC over said reinforcing sheet and curing said layers under heat and pressure in such mold to form each impact resistant skin.

[0009] In addition the invention includes the door with high impact resistance as defined along with a window light also have high impact resistance wherein the window light includes a sheet of tempered glass adhered to a sheet of polycarbonate, second sheet of tempered glass and a specific frame separating the two sheets of tempered glass along with a seal means about the perimeter of this assembly with the frame and sealing means cooperating so that the perimeter of the sheets can articulate as the central portions thereof flex.

DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a plan of the novel door according to this invention with a small part of the surface broken away to illustrate the flexible reinforcing sheet (not to scale) sandwiched in each skin;

[0011]FIG. 2 is a section along line 2-2 of FIG. 1 with central parts broken away, illustrating the internal components of the novel door;

[0012]FIG. 3 is a section along line 3-3 of FIG. 1, with central parts broken away, again illustrating the internal components of the novel door:

[0013]FIG. 4 is a plan of the door shown in FIG. 1 with a widow light which also has higher impact resistance to complement the door;

[0014]FIG. 5 is a cross section of the novel window light shown in FIG. 4;

[0015]FIG. 6 is an alternate embodiment of the window light in cross section; and

[0016]FIG. 7 is a cross section of the aluminum frame used in forming the impact resistant window light.

DESCRIPTION OF AN EMBODIMENT

[0017] The present invention addresses the problem of the failure of prior art synthetic doors under the Dade County criteria by forming novel skins in a built up or layered structure prior to the application of heat and pressure to cure the skin. More particularly, in a mold for forming a skin according to this invention, a conventional SMC for door applications [such as described in U.S. Pat. No. 5,934,040] is placed in the mold as a first layer. The second layer in the mold is a flexible sheet of reinforcing sized to cover the entire first layer. This flexible sheet is preferably a glass fiber cloth, but also may be selected from glass fiber chopped strand mat, glass fiber continuous strand mat, glass fiber filament mat or glass fiber roving mat. At least one flexible sheet is employed and the thickness of the sheet or sheets employed should be approximately 0.22 mm. After the sheet or sheets have been placed in the mold, clinker glass fibers are evenly dispersed over the sheet forming another layer, followed by a final layer of SMC material.

[0018] Once the layered components are in the mold, the mold is closed and heat and pressure is applied to cure the SMC. Typically the preferred SMCs are, by weight of polyester resin 12% to 15%, polystyrene 5% to 15%, inert fillers 40% to 50% and chopped fiber glass 15% to 25%. Curing in the compression molding machine is carried out at pressures from 600 to 1,500 psi for a cure period from 60 to 200 seconds at a temperature from 300 to 400 degrees. As indicated herein, the mixtures are usually referred to as sheet molding compounds [SMCs] and are thermoset materials, including phenolics, urea, melamines, polyolefins and polyesters, the latter being more common. A general description of the sheet molding process is found in an article entitled, “Compression Molding” by N. D. Simons in Modern Plastics Encyclopedia, Vol. 54 No. 10A (197778) and is well known in the art of constructing such doors.

[0019] Typically the skins of prior art synthetic doors are from 0.05 to 0.20 inches [1.27 to 5.08 mm] in thickness. The thickness of the skins made according to the current invention are around 5.0 mm in thickness and may have graining on the exterior surfaces, if the pattern is provided in the mold cavity. In general the first layer of the SMC is from 0.10 to 2.00 mm in thickness followed by one or more flexible reinforcing sheets having a joint thickness of approximately 0.22 to 0.8 mm. Thereafter the clinker glass layer is applied in a thickness of from 0.10 to 2.00 mm, followed by a layer of SMC from 0.10 to 2.00 mm all layers approximating 5.0 mm in thickness. In general the flexible reinforcing sheet will be 3% to 40% of the thickness of the final skin thickness.

[0020] The skins produced by the forgoing process have much higher impact resistance than the conventional synthetic door skins and, as indicated, when assembled on a door frame as herein after described, passed the criteria for Dade County, Florida.

[0021] As to the actual door construction according to this invention, reference is made to FIGS. 1, 2 and 3 illustrating such assembly. As can be seen, this door 10 has exterior skins 11 and 12 which are formed by the laminating process described above. For purposes of illustration in FIG. 1 the skin 11 is peeled away to show the reinforcing sheet 13 which is not shown to scale but for illustration only. These skins are glued to a rectangular frame composed of the rails 14 and stiles 15 of the door, see FIGS. 2 and 3 (the glue and gluing process of assembly are well know in the synthetic door art). As both skins are glued to the frame [composed of the rails and stiles] a hollow core 16 is formed between the two skins 11 and 12 and about the inside perimeter of the frame. This core is filled with a plastic foam 17 for added strength. Commercially available, high density polyurethane foams are capable of foaming at relatively low temperatures, and expand to a density of approximately 2 pounds per cubic foot in the core to complete the door structure. Other foam may used however, even though polyurethane foam is used in the preferred embodiment of the door product of the invention. The rails and stiles can be composed of wood or an extruded plastic and are joined where they meet to form the corners of the frame. Plastic foam extrusions, such as those described in U.S. Pat. No. 6,380,272 issued to Chen are suitable for the rails and stiles of the door.

[0022] In the past, impact resistance of SMC skins and/or products have been increased by using more expensive resins, such as polyolefins and the like. However according to this invention the appropriate strength can achieved with polyester resins using the layered technique, as defined in this invention.

[0023] Often these synthetic doors employed as the means of ingress and egress to residential and or commercial structures have window lights, such as show in FIG. 4 where the door illustrated in FIG. 1 is equipped with window light 20. Obviously, if the window light in a synthetic door does not comply with the criteria set up by Dade County for impact resistance, the entire door fails.

[0024] According to this invention a special window light is provided which will pass the criteria of Dade County when installed in the novel door of this invention, which novel window light is illustrated in FIGS. 5 and 6.

[0025] As can be seen in FIG. 4 a window light 30 is provided in the novel door illustrated in FIG. 1. This is accomplished by cutting a suitable aperture in the door described and installing a window frame 31, such as the window frame illustrated in U.S. Pat. No. 5,249,403 issued to Neilly et al along with installing a novel window light illustrated in FIG. 5 or FIG. 6 in the window frame. Generally the prior art window lights did not pass the tests of Dade County specified above while the novel designs for window lights illustrated in these figures did not have any problems meeting the criteria along or when installed in a door as described.

[0026] More particularly referring to FIG. 5, the novel window light 30 is composed of a sheet 32 of tempered glass which is bonded to polycarbonate sheet 33. This bonding is accomplished with an acrylic adhesive film or a polyurethane adhesive film between the sheet of tempered glass and the polycarbonate sheet, the latter sheet sized to leave margins 34 of the tempered glass about the perimeter of the polycarbonate sheet. Once the tempered glass and polycarbonate sheet are assembled they are placed in a closed furnace with uniform pressure applied to resulting laminate to insure a satisfactory bond. Laminated safety glass is described in U.S. Pat. No. 3,888,032 which comprises polycarbonate reinforced glass wherein the polycarbonate and glass are bonded to one another by an interlayer of aliphatic polyurethane. Polyurethane is opined to provide sufficient adhesion between the glass and to the polycarbonate, eliminating stress cracking, delimitation and or cloudiness. The process defined according this invention achieves the same results.

[0027] After the laminate is removed from the furnace a special aluminum frame 35 is mounted on the surface and about the perimeter of the polycarbonate sheet. Thereafter a second sheet 36 of tempered glass, having the same dimensions as the first sheet 32 of tempered glass, is mounted on the top of the aluminum frame as can be seen in FIG. 5. The frame is formed of aluminum rectangular tubing and separates the polycarbonate sheet from the second sheet of tempered glass by at least one eighth of an inch [0.005 mm]. The frame is not limited to the preferred aluminum tubing construction and can be made of other materials.

[0028] As can be appreciated from FIG. 5, the above described assembly leaves a groove 37 between the two sheets of tempered glass about the perimeter of the assembly. This groove is filled with pre-heated butyl adhesive 38 to complete the novel window light in a sealed unit. The sheet of tempered glass with the sheet of polycarbonate adhered thereto is the strongest pane of the light and therefore is positioned in the window frame 31 to be on the exterior of the door 10.

[0029] A second embodiment of the window light is illustrated in FIG. 6 which has increased impact resistance. In its construction the laminate of the tempered glass 32 and polycarbonate sheet 34 includes an additional sheet of tempered glass 39 mounted on top of the polycarbonate sheet and dimensioned to the same size as the polycarbonate sheet. These pieces are bonded together with acrylic adhesive or the like and are placed in a furnace as previously described with a uniform pressure applied to the laminate while it is heated to insure a high bond strength between the components of this laminate.

[0030] After this three piece laminate is removed from the furnace, the aluminum frame 35 is mounted on the surface of the additional sheet 39 of tempered glass about its perimeter. Thereafter the second sheet 36 is mounted on the top of the aluminum frame as described above. Since the first and second sheets of tempered glass have a larger perimeter dimension than the frame, polylcarbonate sheet 34 and the additional sheet 39 of tempered glass, a groove 40 is formed about the perimeter of this assembly. To complete this assemble a preheated butyl adhesive 38 is forced into this groove to seal the entire assemble about its perimeter.

[0031] The interior space between the several panes can be filled with dry gas to prevent condensation between them as the surfaces of the window light experience variation in temperatures.

[0032] From the cross section of the aluminum frame shown in FIG. 7 a feature of the invention can be seen which is that frame has reliefs 41 and 42 at its top and bottom which allow the butyl adhesive 38 to fill and leaving a reduced area at the top and bottom of the frame members. Moreover the top and bottom of the frame is not bonded to the glass and or polycarbonate sheets. As a result as the center of the panes flex in and out the top and bottom of the frames act as a fulcrum and elasticity of the butyl adhesive allows the perimeter of the panes (sheets) to move slightly as the central portions of the panes move in and out, avoiding additional stresses therein.

[0033] This window light can be mounted in window frame 31 in the door 10 with the three piece laminate of the light on the outside or exterior of the door as it is the strongest pane of the light.

[0034] The forgoing description is by way of illustration and not by way of limitation. 

Having Described my Invention, I claim:
 1. An improved synthetic door having high impact resistance comprising: a rectangular frame forming the rails and stiles of said door; a pair of skins, one skin glued to one side of said frame and the other skin glued to the other side of the frame forming a hollow cavity between said skins and the inside perimeter of said frame; each of said skins being formed with a flexible sheet reinforcing sandwiched between layers of its SMCs; and plastic foam filling such cavity.
 2. The improved synthetic door in claim 1 wherein the SMC is, by weight, 12% to 15% polyester resin, 5% to 15% polystyrene and 40% to 50% inert fillers and 15% to 25% chopped fiber glass.
 3. The improved synthetic door in claim 1 where the flexible reinforcing sheet is a sheet of glass cloth which is sized to extend throughout its associated skin.
 4. The improved synthetic door in claim 1 where the flexible reinforcing sheet is selected from the group consisting of fiber glass cloth, glass fiber chopped strand mat, glass fiber continuous strand mat, glass fiber filament mat and glass fiber roving mat, said sheet extending throughout its associated skin.
 5. A method of manufacturing a high impact resistant skin for a synthetic door comprising the steps of: placing a layer of SMC in a compression mold; placing a flexible reinforcing sheet over said layer of SMC; placing a second layer of SMC over said reinforcing sheet, and curing said layers under heat and pressure in such mold to form the impact resistant skin.
 6. The method of manufacturing a high impact resistant skin defined in claim 5 wherein the SMC is, by weight, 12% to 15% polyester resin, 5% to 15% polystyrene and 40% to 50% inert fillers and 15% to 25% chopped fiber glass.
 7. The method of manufacturing a high impact resistant skin defined in claim 5 where the flexible reinforcing sheet is selected from the group consisting of glass fiber cloth, glass fiber chopped strand mat, glass fiber continuous strand mat, glass fiber filament mat and glass fiber roving mat.
 8. The improved synthetic door defined in claim 1 wherein the door has a window frame and a window light mounted in said frame, said window light constructed of a sheet of tempered glass bonded to a sheet of polycarbonate and including a second sheet of tempered glass with a frame separating the sheets of tempered glass and sealing means about the perimeter of said sheets, said frame and sealing mean constructed so that said sheets can articulate at their respective perimeters.
 9. A window light having high impact resistance comprising: a first sheet of tempered glass; a sheet of polycarbonate bonded to said tempered glass; a frame mounted on polycarbonate sheet, said frame having reliefs about its top and bottom edges; a second sheet of tempered glass mounted on said frame, said frame being operable to separate said sheets of tempered glass; and sealing means about the perimeter of said sheets of tempered glass operable to join and seal the assembly so that said frame is joined to the several sheets by said sealing means in said recesses.
 10. A window light having high impact resistance defined in claim 9 wherein the sealing means is a butyl adhesive.
 11. A window light having high impact resistance defined in claim 9 wherein the sheets are joined by a acrylic adhesive and the adhesive is cured by heat. 